Rack mounts on galvalume roof

I am installing a PhotoVoltaic system (solar cells) on a newly installed galvalume roof of a client. The roof is a lap-joint with exposed screws with flats approx. 4 inches wide with raised ridges in between. The PV system is mounted on a rack-mount frame that comes with 'L - feet' which are basically 1/8 inch aluminum angle with a mounting surface of about 1-1/2 inch square and a hole for 5/16 lag screws. I need to attach these (16 in all) to the face of the roof.
How can I mount these without causing leaks or other problems in the roof?? Are there methods of flashing such feet? I can have custom brackets made if necessary.

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With standing seam roofs, there are clips available which lock onto the seams. However, with a through-fastened panel like you're installing, no such clips are available and I would not know of a way to design one either.
I think you'll just have to do fasteners through the roof panels, much like their own fasteners. I would pre-drill the holes in the roofing. When you possition your L Bracket, put a good bed of high quality butyl rubber caulk between the bracket and the metal roof. This helps seal the penetration and also it will help to separate the dissimilar metals. I would also paint at least the underside of the L Bracket with a couple of coats of a quality coating. There is a product out called ECK which you can find on the internet. ECK offers superior protection between dissimilar metals.
I would use only stainless steel screws for the final attachment. I would use a cap-head style of screw and then put a neoprene washer beneath the cap.
After that, hope for the best. Like any roof penetration, there is risk involved.
Good luck.

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im putting on a galvalume roof and am thinking of putting photovoltaic panels. any sites or info you can tell me about. am also unsure if the galvalume panels go directly screwed to the roof or 1 by 4s put on tar paper or vapor barrier thus creating an airspace. i do have an attic.. was told no need to put the 1 by 4's.

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A strong, leak resistant method is to install 1-5/8" aluminum unistrut to the galvalume roof pulins, then attach your L-feet and rails making a cross hatch arrangement. Unistrut runs E-W along purlins and solar rails run N-S. This adds cost but will give you a very solid foundation and keeps all your roof penetrations on the high spots of the roofing.
If you have any wind loading issues you need to see a structural engineer.

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S-5! offers a mounting system that has zero penetrations.
The issue of aluminum racking system when attached to a galvalume roof is not really an issue, as long as the surface coating of galvalume is not penetrated.
Galvalume is a zinc-aluminum alloy.

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